The aim of this study was to evaluate the antioxidant properties and total phenolic compounds of a novel peanut-based kefir. HPLC was used to determine the composition of the peanut milk kefir extract. The antioxidant activity of kefir was measured by three methods: DPPH radical-scavenging activity, reducing power, and lipid peroxidation inhibition activity. As results, peanut milk kefir displayed greater antioxidant properties than the milk from which it was formed. Moreover, soluble phenolic content increased with the fermentation of peanut milk using kefir culture. Two groups of phenolics (phenolic acids and flavonoids) were found in peanut-based kefir extract.